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      <title>如何在 SpringMVC中实现文件上传和下载 - 交互式测验</title>
      <style>
        @import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@400;500;700&display=swap');
        
        body {
          font-family: 'Noto Sans SC', sans-serif;
          background-color: #f4f7f9;
          color: #333;
          display: flex;
          justify-content: center;
          align-items: center;
          min-height: 100vh;
          margin: 0;
          padding: 20px;
          box-sizing: border-box;
        }
        
        .main-wrapper {
            position: relative;
            width: 100%;
            max-width: 900px; /* Wider to accommodate buttons */
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .quiz-container {
          background-color: #ffffff;
          border-radius: 16px;
          box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
          width: 100%;
          max-width: 700px;
          overflow: hidden;
          z-index: 10;
        }

        .quiz-header {
          background-color: #4a90e2;
          color: white;
          padding: 20px 30px;
          text-align: center;
        }

        .quiz-header h1 {
          margin: 0;
          font-size: 24px;
          font-weight: 700;
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        .quiz-header p {
            margin: 5px 0 0;
            font-size: 14px;
            opacity: 0.9;
        }

        .quiz-body {
          padding: 30px;
        }

        .progress-bar {
            display: none; /* 隐藏进度条 */
            width: 100%;
            background-color: #e0e0e0;
            border-radius: 5px;
            height: 10px;
            margin-bottom: 20px;
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        #progress-indicator {
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            background-color: #4caf50;
            border-radius: 5px;
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        #question-container {
          margin-bottom: 20px;
        }

        #question-text {
          font-size: 18px;
          font-weight: 500;
          line-height: 1.6;
          margin-bottom: 25px;
        }

        .options-list {
          list-style: none;
          padding: 0;
          margin: 0;
        }

        .option-item {
          background-color: #f8f9fa;
          border: 1px solid #dee2e6;
          border-radius: 8px;
          padding: 15px;
          margin-bottom: 12px;
          cursor: pointer;
          transition: background-color 0.2s ease, border-color 0.2s ease;
        }

        .option-item:hover {
          background-color: #e9ecef;
        }
        
        .option-item.selected {
            background-color: #d1e7fd;
            border-color: #4a90e2;
        }

        .quiz-footer {
          padding: 20px 30px;
          display: flex;
          justify-content: space-between; /* 将按钮分布在两侧 */
          align-items: center;
          min-height: 65px; /* Reserve space */
        }

        .nav-btn {
          background-color: #4a90e2;
          color: white;
          border: none;
          border-radius: 8px;
          padding: 10px 20px;
          font-size: 16px;
          font-weight: 500;
          cursor: pointer;
          transition: background-color 0.2s ease, transform 0.2s ease;
          box-shadow: 0 4px 12px rgba(0,0,0,0.15);
        }
        
        #next-btn {
            background-color: #28a745;
        }

        .nav-btn:hover {
          background-color: #357abd;
          transform: scale(1.05);
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        .nav-btn:disabled {
            background-color: #a0c3e8;
            cursor: not-allowed;
            opacity: 0.7;
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        #result-container {
            border-top: 1px solid #eee;
        }
        
        .result-box {
            border-radius: 8px;
            padding: 20px;
            margin-top: 20px;
        }
        
        .result-box.correct {
            background-color: #d4edda;
            border: 1px solid #c3e6cb;
            color: #155724;
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        .result-box.incorrect {
            background-color: #f8d7da;
            border: 1px solid #f5c6cb;
            color: #721c24;
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        .result-box h3 {
            margin-top: 0;
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        .explanation-text {
            margin-top: 15px;
            line-height: 1.7;
        }
        
        .source-text {
            font-style: italic;
            font-size: 14px;
            margin-top: 15px;
            color: #555;
        }

        
        .final-score-container {
            padding: 40px;
            text-align: center;
        }
        .final-score-container h2 {
            margin-top: 0;
            margin-bottom: 30px;
        }
        .score-summary {
            display: flex;
            justify-content: center;
            gap: 20px;
            margin-bottom: 40px;
            flex-wrap: wrap;
        }
        .score-card {
            background-color: #f8f9fa;
            border-radius: 12px;
            padding: 20px;
            width: 180px;
            box-shadow: 0 4px 12px rgba(0,0,0,0.05);
            border: 1px solid #e9ecef;
        }
        .score-card h3 {
            margin: 0 0 10px;
            font-size: 16px;
            font-weight: 500;
            color: #555;
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        .score-card p {
            margin: 0;
            font-size: 28px;
            font-weight: 700;
            color: #333;
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        .score-details table {
            width: 100%;
            font-size: 16px;
        }
        .score-details td {
            padding: 4px 0;
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        .score-details td:last-child {
            text-align: right;
            font-weight: 700;
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        .report-actions button {
            background-color: #fff;
            border: 1px solid #ccc;
            border-radius: 8px;
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        .report-actions button:hover {
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        .hint-container {
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            padding: 15px;
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            color: #006064;
            font-size: 15px;
            line-height: 1.6;
            display: none; /* 默认隐藏 */
        }
      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>如何在 SpringMVC中实现文件上传和下载 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "在Spring MVC中，`MultipartResolver` 组件的核心职责是什么？",
    "options": [
      "解析HTTP请求中的multipart/form-data数据，并将上传的文件封装成 `MultipartFile` 对象。",
      "直接将文件内容写入服务器的物理磁盘以完成存储。",
      "在服务器端验证上传文件的MIME类型是否符合安全规范。",
      "管理文件下载时的数据流传输，确保数据完整性。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "`MultipartResolver` 是Spring MVC处理文件上传的核心组件。它的主要作用是拦截 multipart 请求，将其内容解析出来，并将文件数据包装成一个易于在Controller中操作的 `MultipartFile` 对象。后续的存储或验证逻辑是在Controller中完成的，而不是`MultipartResolver`的职责。",
    "source": "文档中「1.1 配置 MultipartResolver」部分",
    "hint": "文档中提到：Spring MVC 通过 `MultipartResolver` 处理文件上传，它负责将 HTTP 请求中的文件解析成 `MultipartFile` 对象。"
  },
  {
    "question": "根据文档，哪项是关于文件上传存储位置的最佳安全实践？",
    "options": [
      "将文件存储在项目的 `src/main/resources/static` 目录下以便于访问。",
      "将文件存储在Web应用无法直接公开访问的目录，或使用云存储服务。",
      "直接以用户上传的原始文件名保存在服务器根目录。",
      "将文件存储在数据库的 Varchar 类型字段中。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "为了安全起见，应避免将上传的文件存放在 Web 可直接访问的目录下（如Web根目录或静态资源目录），因为这可能导致恶意用户通过URL直接执行或访问这些文件。推荐的做法是存储在非公开目录、数据库或专用的云存储服务（如AWS S3）中。",
    "source": "文档中「1.3 文件上传注意事项」部分的 “安全性” 条目",
    "hint": "思考一下：如果把用户上传的脚本文件直接放在Web目录下，会发生什么？文档建议“避免将上传文件直接存储在 Web 目录下”。"
  },
  {
    "question": "在实现文件下载功能时，设置哪个HTTP响应头（Header）的 `attachment` 值可以提示浏览器将内容作为附件下载，而不是尝试直接在页面上显示？",
    "options": [
      "Content-Type",
      "Content-Length",
      "Content-Disposition",
      "X-Download-Options"
    ],
    "correctAnswerIndex": 2,
    "explanation": "将 `Content-Disposition` 响应头的值设置为 `attachment; filename=\"...\"` 是实现文件下载的标准方式。它明确告诉浏览器，响应体应被视为一个需要下载的附件，而不是在浏览器窗口内联显示的内容（例如图片、PDF或HTML）。",
    "source": "文档中「2.2 文件下载注意事项」部分的 “响应头设置” 条目",
    "hint": "文档中提到一个关键的响应头设置，它的值被设为 `attachment`，用于“提示浏览器以附件形式下载文件”。"
  },
  {
    "question": "文档中提到了处理大文件下载时应注意什么，以避免服务器内存溢出（OOM）？",
    "options": [
      "临时增大应用服务器的JVM堆内存（Heap Size）来容纳大文件。",
      "在下载开始前，将整个文件内容加载到一个 `byte[]` 数组中以加快传输。",
      "将大文件压缩成zip格式再进行传输，以减少网络带宽。",
      "使用流式处理将文件数据分块写入响应输出流，而不是一次性将整个文件读入内存。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "对于大文件，如果一次性将其全部读入内存，当并发下载请求增多时，极易导致服务器内存耗尽并发生溢出。正确的做法是使用输入/输出流（Streaming），边从磁盘读取文件数据边写入HTTP响应流，这样内存中只需要保留一小部分数据缓冲区即可。",
    "source": "文档中「2.2 文件下载注意事项」部分的 “大文件处理” 条目",
    "hint": "文档强调“在服务器端使用流式处理避免将整个文件加载到内存”。"
  },
  {
    "question": "为了防止文件下载功能中的“路径注入”或“目录遍历”攻击，文档建议了哪种安全措施？",
    "options": [
      "对客户端传递的文件名进行URL编码，以消除特殊字符。",
      "不直接使用客户端传递的文件名或路径，而是通过一个安全的ID或哈希值来映射到真实的文件存储路径。",
      "使用正则表达式严格限制文件名只能包含字母和数字。",
      "将文件存储目录的服务器文件系统权限设置为只读。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "如果直接使用用户传入的参数（例如 `../../etc/passwd`）来拼接文件路径，攻击者就可能访问到非预期的敏感文件。最佳实践是，不信任任何用户输入。通过ID映射，后端可以从数据库或一个安全的映射表中查找真实的文件路径，从而完全杜绝目录遍历的风险。",
    "source": "文档中「3.1 安全性」部分的 “路径注入攻击” 条目",
    "hint": "文档建议：“避免客户端直接提供文件路径...建议使用 ID 或者哈希值映射到具体文件。”"
  },
  {
    "question": "当面临高并发的文件上传或下载场景时，文档推荐采用哪种方式来提升系统性能和响应能力？",
    "options": [
      "在Controller方法上添加 `synchronized` 关键字，确保每次只有一个文件在处理。",
      "为服务器配置更多的CPU核心和内存资源。",
      "引入异步处理或消息队列，将文件I/O操作与主请求处理线程解耦。",
      "使用Nginx作为反向代理，直接处理所有文件传输。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文件I/O是耗时操作，在高并发场景下，同步处理会长时间占用处理请求的Web线程，导致系统吞吐量下降。通过异步处理或消息队列，可以将耗时的I/O任务交给后台的线程或工作进程来完成，主线程可以迅速返回响应，从而提高系统的整体性能和用户体验。",
    "source": "文档中「3.2 并发与性能」部分的 “异步处理” 条目",
    "hint": "文档中明确指出，对于并发场景，应“考虑使用异步请求或消息队列，避免阻塞主线程”。"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
        let currentQuestionIndex = 0;
        let score = 0;
        // 存储每个问题的回答状态
        const userAnswers = new Array(quizData.length).fill(null); 

        const questionTextEl = document.getElementById('question-text');
        const optionsListEl = document.getElementById('options-list');
        const resultContainerEl = document.getElementById('result-container');
        const quizContentEl = document.getElementById('quiz-content');
        const progressIndicatorEl = document.getElementById('progress-indicator');
        const prevBtn = document.getElementById('prev-btn');
        const nextBtn = document.getElementById('next-btn');
        const hintBtn = document.getElementById('hint-btn');
        const hintContainerEl = document.getElementById('hint-container');

        function loadQuestion() {
          resultContainerEl.innerHTML = '';
          optionsListEl.innerHTML = '';
          hintContainerEl.style.display = 'none'; // 隐藏提示
          
          if (currentQuestionIndex >= quizData.length) {
            showFinalScore();
            return;
          }

          updateProgress();

          const currentQuestion = quizData[currentQuestionIndex];
          questionTextEl.textContent = `(${currentQuestionIndex + 1}/${quizData.length}) ${currentQuestion.question}`;
          
          currentQuestion.options.forEach((optionText, index) => {
            const li = document.createElement('li');
            li.className = 'option-item';
            li.textContent = optionText;
            li.dataset.index = index; // Store index in a data attribute
            // 如果这道题已经回答过，恢复状态
            if (userAnswers[currentQuestionIndex] !== null) {
                if (index === userAnswers[currentQuestionIndex]) {
                    li.classList.add('selected');
                }
            }
            optionsListEl.appendChild(li);
          });

          // 如果已经回答过，直接显示结果
          if (userAnswers[currentQuestionIndex] !== null) {
              const isCorrect = userAnswers[currentQuestionIndex] === currentQuestion.correctAnswerIndex;
              showResult(isCorrect, currentQuestion);
          }
          
          updateNavigationButtons();
          updateProgress();
        }

        function selectOption(optionIndex) {
            userAnswers[currentQuestionIndex] = optionIndex;
            const currentQuestion = quizData[currentQuestionIndex];
            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
            score = userAnswers.reduce((acc, answer, index) => {
                return answer === quizData[index].correctAnswerIndex ? acc + 1 : acc;
            }, 0);

            showResult(isCorrect, currentQuestion);
            updateNavigationButtons();
        }
        
        function updateProgress() {
            const answeredQuestions = userAnswers.filter(answer => answer !== null).length;
            const progressPercentage = (answeredQuestions / quizData.length) * 100;
            progressIndicatorEl.style.width = `${progressPercentage}%`;
        }
        
        function updateNavigationButtons() {
            prevBtn.style.display = 'block';
            nextBtn.style.display = 'block';
            hintBtn.style.display = 'block'; // 显示提示按钮

            prevBtn.disabled = currentQuestionIndex === 0;
            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
            nextBtn.textContent = (currentQuestionIndex === quizData.length - 1) ? '查看报告' : '下一题';
            
            // 如果当前问题没有提示，则禁用提示按钮并隐藏提示内容
            if (!quizData[currentQuestionIndex].hint) {
                hintBtn.disabled = true;
                hintContainerEl.style.display = 'none';
                hintContainerEl.textContent = ''; // 清除旧的提示内容
            } else {
                hintBtn.disabled = false;
            }
        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
            Array.from(optionsListEl.children).forEach((child, index) => {
                child.style.pointerEvents = 'none';
                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
                    child.style.backgroundColor = '#f8d7da';
                    child.style.borderColor = '#f5c6cb';
                }
            });
        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
                currentQuestionIndex--;
                loadQuestion();
            }
        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  